This invention relates in general to impact printers with wheel-type print elements and more particularly to the means and methods for enhancing the ribbon lift function during operation of the printer.
The Diablo Corporation, a subsidiary of the present assignee, is marketing a serial printer under the tradename of Diablo Hytype I which employs a movable carriage with a daisy-type print wheel, print hammer and ribbon cartridge mounted thereon. A printer of this type is disclosed in a U.S. patent application filed Sept. 4, 1973, in the name of Andrew Gabor, Ser. No. 394,072, entitled "High Speed Printer with Intermittent Print Wheel and Carriage Movement", being a continuation of an application filed Feb. 25, 1972, Ser. No. 229,314, both now abandoned, the disclosure of which is incorporated by reference into this specification.
The Diablo Hytype I printer is enjoying commercial success as a serial printer in such applications as communication terminals, computer output devices, etc. However, in certain type applications, such as automatic text-editing typewriter applications in the office environment, additional features and capabilities are desired, e.g., higher print quality. In the text-editing or office-typing environment, the demands for high print quality cause the print wheel to be subjected to about ten times greater force due to about five times greater hammer energy compared to a Hytype I printer operating as a computer output terminal, for example.
A modified model of the Hytype I printer is employed as the printing mechanism of the commercially available Xerox 800 Electronic Typing System for automatic text-editing typewriter applications in the office environment. To provide the high print quality needed, the integrally molded thermoplastic print wheel of the Hytype I printer was replaced by a composite print wheel, such as that disclosed in a U.S. patent application, filed Sept. 25, 1974, in the name of Gordon Sohl et al., Ser. No. 509,193. In addition, a different print hammer assembly was incorporated therein which provided greater hammer energy. A card guide was added to the carriage to provide assistance in the operation of inserting and aligning paper in the automatic text-editing typewriter. The Diablo Hytype I ribbon cartridge containing a fabric ribbon was replaced by a ribbon cartridge containing a matrix-type plastic ribbon from which a higher quality of printed material may be obtained.
In the environment provided by the modified printer, when the matrix-type plastic ribbon was impacted between the character slug of the print wheel and the paper, the plastic ribbon tended to curl or become cup-shaped around a longitudinal centerline of the ribbon. The upper and lower edges of the plastic ribbon curled toward the print wheel. The spacings between the paper, ribbon and composite print wheel are extremely close because of the modification (addition of a card guide and the thicker character slugs of the new composite print wheel) to the printer and on occasions the curled edge or edges of the plastic ribbon would make contact with the print wheel while the print wheel was rotating to the next print position. When this type of contact occurred, the plastic ribbon could, on occasions, be prevented from lifting or completely lifting to its print position, from its lower rest position, resulting in the loss of that particular character or the cropping of the upper portions of the character or characters.
With these prior art problems in mind, it is a primary object of the present invention to provide a means and method for enhancing the ribbon lift function and thereby reduce printing malfunctions.
Another object of this invention is to provide a means and method for enhancing the ribbon lift function of a print wheel impact printer along the presently described vane.
Other objects and advantages will be evident from the specification and claims when read in conjunction with the accompanying drawing illustrative of the invention.